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Paint-on Laser Brings Optical Computing Closer
holy_calamity writes "New Scientist has a story about a laser made by painting a solution of semiconductor crystals onto glass. It could be used to break the interconnect barrier by having optical interconnects, the interconnect barrier threatens Moore's law unless a faster way of connecting chips is found."
Is there any chance this paint is waterproof.
Sincerely,
Dr Evil.
liqbase
Optical interconnects could make for far more reliable connections between system components. Ribbon cables etc break easily, and are a real nightmare for assembly. OTOH, a few specks of dust in an optical connection could cause a lot of grief (reflection etc) making one wonder what the longterm prospects of shipping optically connected products are.
Engineering is the art of compromise.
It is the same thing, but the media is different.
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Across the abundant natural forms of light-conducive media like atmosphere or empty space, very much so.
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it propagates faster than electricity. The individual electrons get hung up on imperfections in the conductor they travel along making them travel considerably slower than the speed of light. Does that matter in today integrated circuits? I'm pretty sure it isn't a problem. ;)
It is not the travelling of electrons that gets the electric signal propagating.
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First comment already did the joke. And better.
Google has failed me, turning up references to it but nothing about it.
So can someone explain what it is... and what exactly the problem is?
Technology, the cause of and solution to all of life's problems.
But, will we have 5 megawatts by mid-May?
Also, electricity suffers resistance when it travels through metal, creating HEAT and LOTS of it (I've heard its not uncommon for the latest P4's to operate around 70dec C under full load with stock cooler). Light on the other hand, travelling through optical cable or through air or vacuum, is offered no resistance (or so little that it barely generates any appreciable heat).
Room temperature processors anyone? This would be great for eliminating the wear and tear and thermal breakdown caused by heating/cooling when turning your comp on and off. I believe the speed difference between electricity and light (while it may be significant through specific mediums) would be negligible? We're talking distances of micrometers, and 2 or 3 cm at worst (think of the size of a processor die).
Chums up, let's do this!
exactly. so, while the speed of light through a vacuum, or even air is considerably faster, it doesn't effect the speed of the signal propagating through the circuit.
It is not the travelling of electrons that gets the electric signal propagating.
.25 and .75c
(IIRC, hams use a factor of around .7c for the speed in a whip
antenna, while tiny ethernet strands only give around .33c).
The travel itself, no. The wavefront of "pressure" moving along the path of the electrons, yes. The electrons themselves move at only (depending heavily on current and wire diameter) around 1-10cm per hour.
But the wave still only travels somewhere between
Does the difference there really matter all that much? For long-distance communication, sure. But for chip interconnects? Doubtful.
The article pushing mainly for cost-effectiveness.
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Now I will have to build a new Flux Capacitor!
"The observation made in 1965 by Gordon Moore, co-founder of Intel, that the number of transistors per square inch on integrated circuits had doubled every year since the integrated circuit was invented. Moore predicted that this trend would continue for the foreseeable future. In subsequent years, the pace slowed down a bit, but data density has doubled approximately every 18 months, and this is the current definition of Moore's Law, which Moore himself has blessed. Most experts, including Moore himself, expect Moore's Law to hold for at least another two decades."
It has to do with transistors.. not the speed of processors.
There are frequency limitations to the speed at which processors can be run. Something about crossover fields at frequency or some such.
Light would have the ability to be switched much more quickly, but if you're going to switch it with electricity based circuits.....
yes. inductance slows electrons down and electrical traces can't touch each other so they have to be drawn around each other - laser light beans can pass through one another with no interference. So the traces can be more direct and hence faster. Finally, the scale of components in a processor has gotten small enough that individual traces are interfering with one another inductively and on a quantum level - these don't happen with light.
You are checking your backups, aren't you?
The intention of quantum computing is not to replace, but rather to complement classical (i.e. digital) computing. Quantum computing can dramatically speed up certain tasks, such as cryptography and searching. Even though they cannot yet be implemented, a number of important quantum algorithms have already been discovered. Most - but not all - quantum algorithms return probabilistic answers, rather than clear-cut answers as most classical algorithms do.
Shor's algorithm for factoring numbers could be used to rapidly crack RSA encryption. http://en.wikipedia.org/wiki/Shor's_algorithm
Grover's algorithm can be used to search an unsorted database in O(n?2) time. http://en.wikipedia.org/wiki/Grover's_algorithm
The article and summary seem to be a bit misleading and vauge about how the speed increase arrises. The great benefit of optical computing is that it allows the signals to get much much closer together than electronic circuits, and as such allow more compact circuits, which as we know generally means faster. Interestingly, electronic signals in wires and optical signals in fibers have roughly identical upper speed limits (light in free-space optical computers is faster, but also almost impossible to do anything useful with), so its the density which is the major factor.
Electrons are charged, so as you squeeze transistors closer together, the wires get thinner and closer together, and you get cross-talk and interference between them. Photons however hardly interact at all, so you can have many beams in the same space, and theres very little heat to be dissipated. Multiplw frequencies can also be used, resulting in massivly parallel computing (another GoodThing).
There are downsides with optical computing still, photons cannot be stopped and stored (easily), meaning any kind of useful computer in the near term is likely to be some sort of electro-optical hybrid, with photons carrying signals and electrons storing them
it wouldn't be that hard to change it from binary (light on/light off) to amounts of light (of course the same thing could be done with electric interconnects but by voltage--just not as consistently)
Didn't the Russians try this at one point? If I remember right, they had trouble distinguishing between the on state, and the not on/not off state, and wound up abandoning the idea because it was too unreliable.
Yes and no. It depends on what the electricity is traveling through (freespace? wire?). Electricty generates heat and noise. Now assuming it takes less electricity to power the lasers then it will generate less heat. I think noise is the main reason. Two wires (general term, wires...traces..) with current flowing through them will affect each other, hence putting noise on each others line. This is ok at low frequencies (slow speeds), but at higher frequencies it distorts the signal up to a point of unusability. So if you replace your wires with light you dont have this problem because two light pipes next to each other will not affect each other. There is a reason why they use optical switching for the internet backbone, its fast (not just because the end product has to be light going through fiber optic cables). The problem these switches right now have to be maid out of exotic materials and cannot be integrated on a chip. Using optical switches inside of a chip is the holy grail. Don't underestimate the importance on advancing optics. If you want computers to keep getting faster we will have to go to optical pretty soon . Within the next 10 years we are expected to hit a barrier with current technology. You watch. Optical will be beating at your door before you know it.
There have been experiments with different voltages to distinguish more than just on/off (although I don't know if it was done by the Russians), and from what I've heard/read such experiments have proven less than successful because the voltage/currency/whatever isn't always consistent (power spikes and such). Unless you're talking about the light on/off thing--in which case I don't know, but it shouldn't be too hard to determine just the on/off state (as that's basically how fiber optic cables work from my very limited understanding of them). In soviet russia hypothesis test you!
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Electricity is electrons. Electrons have mass (though extremely small). According to Einstein, nothing with mass can travel at the speed of light. Therefore, yes, light is faster than electricity.
What'chu lookin' at Willis?
Electricity in standard copper is about 60% the speed of light in a vacuum. If my memory is right...
Slashdot.. where people join together in deliberate ignorance.
The bottleneck in computing isn't Moore's Law of transistor density. It's programming paradigms. We're wasting the vast majority of processing/memory/transmission capacity with linear programming, rather than parallel programs. Procedural programs are based entirely on the bottleneck paradigm, with the entire system reduced to a single boolean operation at any given time. Any parallelism is exceptional, and difficult to express in the symbols humans send to computers.
Parallel dataflow and distributed control are long overdue to the mainstream. Compilable UML is a slow, crude path to it. When I can draw a flowchart of primitive objects, any of which are packaged procedures or other flowed objects, and watch it run, I'll have a much better shot at exploiting all the compute/storage/transmit capacity available at that time. When "compilers" can distribute my data among the resources according to topology and analytical prediction, I'll finally get full use of the machines I'm using. Until then, I'm doubling my HW capacity every year or two so it can use half the efficiency gain running inefficient software.
--
make install -not war
Well, since electrons are matter, and there happen to be various laws of the universe that are unfriendly to matter moving at the speed of light, I'd have to say probably.
12 steps is too long. My ideal plan is: 1) Quit 2) Relapse 3) ??? 4) Profit!
Moore's Law is only an observation, not a performance goal. Of course it'll go away at some point. Maybe the slowing of density increases points to a maturing of one part of the industry.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
What the hell do imperfections have to do with it? Nothing with mass can move at the speed of light. You seem to be suggesting that if the conductor was perfect, the electrons could move at the speed of light. What sort of crazy talk is that?
Anyway, the electrons have a net speed on the order of just millimeters per second. However, changes in the electric field caused by the motion of the electrons can propagate through the conductor much, much faster.
I recall that a semiconductor engineer mentioned "optical computing" to me at least 20 years ago when I was a kid, and I was thrilled by it. Will this involve the interconnects only, or the whole CPU? Maybe the whole system could be built into an optical chip?
Beauty is in the beholder of the eye.
For example, suppose you wanted something to operate at 10GHz. Now suppose that the medium you use is such that the wave moves at .5c. That gives you a wavelength of just 1.5cm. That means on larger dies, you can start having signal propagation problems, in that you won't get a wave all the way across the chip before the next ones starts. Plays hell on synchronized processor designs like we use today.
It's not a problem yet, that I know of, but something that we have to think about in the future.
From the article: "The resulting device produces a laser beam when a "pump" beam of normal light is shone onto it. This light excites the electrons in the quantum dots up to a higher energy level. When they drop back down to lower energies, the electrons emit light of their own." So the energy source is a $2 flashlight (or an LED, or solar power, etc.)
You are reading a copy of my copyrighted post.
isnt that the reccomended power for Vista?
---- Booth was a patriot ----
That is the mean electron drift velocity, the absolute electron velocity between collisions is on the order of hundred thousand meters per second, depending on the temperature.
That is still a lot slower than the signal propagation velocity, which is comparable to the speed of light (0.7c or so), subject to reactive loading.
Hey, let's go play laser-tag!
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Electrons are practically bystanders in the propagation of a signal down a transmission line. The signal itself is an electromagnetic wave different only in wavelength and frequency from any other electromagnetic wave, including light. They play a crucial role at the ends, but in the middle they just slow things down.
Typical electrical signals are propagated by electromagnetic waves in the wire, not by the electrons themselves. Conduction electron velocity is normally hundreds of times slower than electromagnetic waves in the same material, waves which propagate at healthy fraction of the speed of light (same thing as light actually, just with a different wavelength and a reduced speed due to interaction with the transmission medium).
you relize it's the electromagnetic wave that's travelling, not electrons, right?
The Kruger Dunning explains most post on
A few paragraphs of vague details, then a sophomoric rehash of the last 30 years of semiconductor design. Did New Scientist need some filler material to meet a publishing page quota or something?
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Man I wish I had mod points. Very informative, thank you
What'chu lookin' at Willis?
I had this idea where calculations running at one frequency and calculations running at a non-interfering frequency could be run over the same chip substrate, maybe even more than two frequencies.
Actually, the signal is very, very different from, say, light. Electromagnetic waves (i.e. radiation) can propagate through a vacuum; electronic signals are waves propagating through a medium (i.e. a sea/gas of electrons). People used to think that a wave needed something to propagate through (be it water or electrons), which is not true in the case of light (one recalls Michelson-Morley interferometers). Electronic signals travel extremely fast through wires because the restoring force (the tension, if you want to make an analogy to waves on a string) is very strong compared to mechanical analogs.
> It could be used to break the interconnect barrier by having optical interconnects, the interconnect barrier threatens Moore's law unless a faster way of connecting chips is found.
Actually, it's probably saying that Moore's law will no longer be applicable unless they can manage to break that barrier, which this could help do.
I think the idea is that laser optical interconnects can criss cross each other without interfering, while copper tracks can't. So there is potential for increasing densities, while the roughly 50% propagation speed increase would probably help as well.
Oh well, what the hell...
Well, I guess consumer computing will just remain an "electrifying" experience.
But, can't they make "paint-on" CPUs? I mean, the CPUs and the interconnects are like hand and wrist, right? Well, can they make them of similar "DNA" and part? Or, are they trying not to "kill off" some sacred part of the CPU industry?
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
A better analogy is a tube full of ping-pong balls. Push the ball on one end, and a ball falls out the other. Propagation is nearly instantaneous of great distances, but the electrons themselves hardly move at all.
The higher the technology, the sharper that two-edged sword.
The electrons along the way are certainly affected - but the signal itself is propagated by changes in the electric field. The electric field does not have, nor require any medium - just like light.
More particularly electric signals are not propagated through the sea of free electrons like sound through a gas. The electrons are necessary to deliver actual current at the other end, but the information transfer in a high frequency circuit is virtually all electromagnetic. The electrons vibrate sympathetically, but it is the E-M field that does the work. Collision induced pressure vibrations migrate hundreds of times slower.
The individual electrons get hung up on imperfections in the conductor they travel along making them travel considerably slower than the speed of light. Does that matter in today integrated circuits? I'm pretty sure it isn't a problem.
Actually it IS a problem. Getting the clock signal around a modern CPU is actually pretty tricky as I understand it. (Note Disclaimer.)
The problem is that electrons do flow significantly slower than light, and at close to 4,000,000,000 signals a second, it's absolutely vital to have every item in the core marching to the same drummer. To this end, the clock signal is propagated by several "repeaters" throughout the chip.
I seem to recall doing the math at one point, and when considering the distances involved, its obvious you can't just rely on a single clock generator for an entire CPU.
How many escape pods are there? "NONE,SIR!" You counted them? "TWICE, SIR!"
[i]the interconnect barrier threatens Moore's law[/i]
Terribly sorry to rain on your parade, but the fact that we live in a 3D world with a speedlimit limits computing speed eventually.
Electrical signals in wires travel (according to rough measurements I did about two decades ago) at about 0.3c (a third of the lightspeed). Light travels at 0.6c (in glass).
So you win about a factor of two by moving to light, provided you use fibreglass to channel the communications to the right place.
If you Aim lasers through normal air, you can win a factor of three. Wow. That might extend Moore another 2 years, but it does not solve the fact that physics limits Moore eventually.
In theory, "computing nodes" can be connected using for example hypercubes. 4 nodes form a square with max communications distance of 2, 8 nodes form a cube, with max distance of 3. And so on.
Wether these "computing nodes" are complete computers, elements of a parallel system, or just elements of a CPU, doesn't matter.
As the dimension of the hypercube increases, the physical placement of the nodes in 3D-space means that the communications links between the nodes starts to increase. The Lightspeed limits theoretical computation speed to what you might expect of a 3D structure.
I had been wondering how to create lasers small enough to make a palm-mounted version of a laser-induced-plasma-channel http://en.wikipedia.org/wiki/Laser-Induced_Plasma_ Channel
Now I have it.
Off topic, but had to be asked.
You know, your post was good until you ruined it at the end. I have always wondered, but never bothered to ask until now (irritation level reached its limit?)... What the HELL is the obsession with "first post"? Does it make your dick grow longer if you get it or something? A real, tangible benefit?
Oh, I don't really care about first post. I only put it there because if people DO get it, then somebody seems to always comment about the fact that they DON'T say first post...
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Warning - link contains strong language =)